The present invention is related to the field of forensic science. More particularly, the present invention is related to fingerprint detection and analysis.
Fingerprints are impressions of the system of friction ridges on the surface of fingers, palms, toes, and feet. Most latent fingerprints are formed when perspiration escapes through the ridged surface. The primary component of such a fingerprint is ordinary perspiration. Human perspiration is a mixture of many substances including fatty acids, proteins, peptides, amino acids, chloride salts, water, and urea, some of which can remain detectable on a surface for long periods of time. Fingerprints can also contain residue of what a person has handled. For example, if a person was handling grease, gasoline, TNT, or other substances, the fingerprint may contain trace amounts of these substances.
A variety of methods have been developed which use the various substances contained in the residues of a latent fingerprint for creating an observable image. For example, silver nitrate was found to react with the salt in a latent print, which, through exposure to a light source, forms a visible fingerprint image.
The method widely known as xe2x80x9cdusting for printsxe2x80x9d involves depositing a colored powder on a surface suspected of bearing latent fingerprints. The powder adheres to lipid residue on a surface and the loose excess powder is delicately brushed off, thereby disclosing any latent fingerprints.
In another method, iodine crystals are warmed causing the sublimation of the crystals and the gas thus produced is blown or wafted over the surface being examined for latent fingerprints. Iodine gas reacts with the lipids, causing the latent fingerprint to become visible.
Recent developmental work in the field of fingerprint detection has yielded new detection methods including various fluorogenic visualization and cyanoacrylate (C/A) fuming techniques. In the fluorogenic visualization techniques, the latent fingerprint is treated with one or more chemical reagents which react with and covalently bond with compounds in the print to form a fluorescent chemical product. The image of the latent print is then viewed or photographed with the aid of an optical filter and under illumination of light of appropriate wavelength to cause excitation and fluorescence of the image.
Each of these fingerprint detection techniques relies on the presence of residues from perspiration, which must be present in sufficient quantity to perform the technique. After the sufficient quantity of residue is removed from the surface, the technique can no longer be performed. While more modern techniques require only a small amount of residue, there is still a need for a fingerprint detection technique that would reduce the amount of residue needed to detect latent fingerprints.
Once detected, the fingerprints must be preserved for analysis. One method of preserving the fingerprint is by xe2x80x9cliftingxe2x80x9d the fingerprint from the surface using tape or other material. Another method of preserving the fingerprint is by photographing the fingerprint. While both methods are sufficient for macro analyses by human experts, such as the detection of whorls, arches, and loops, the resolution of the preserved fingerprint is typically not sufficient for use with sophisticated computer algorithms for analyzing micro features of the fingerprint.
The above-described drawbacks and deficiencies of the prior art are overcome or alleviated by a method of detecting fingerprints on a substrate, the method comprising: ion beam mixing materials associated with the fingerprint into the substrate to create an ion beam mixed fingerprint; and analyzing the ion beam mixed fingerprint.
In one embodiment, analyzing the ion beam mixed fingerprint includes optically imaging the ion beam mixed fingerprint. In another embodiment, the analyzing includes scanning the ion beam mixed fingerprint with a scanning electron microscope. In another embodiment, the analyzing includes performing a surface analysis technique on the ion beam mixed fingerprint to identify the chemical composition of at least one material associated with at least one of the fingerprint and the substrate.
In one aspect, the surface analysis technique includes at least one of Auger Spectroscopy, Secondary Ion Mass Spectroscopy (SIMS), Secondary Electron Microscopy (SEM), Particle Induced X-ray Emission (PIXE), and Energy Dispersive X-ray Spectroscopy (EDS).
The analyzing may further include mapping the chemical composition of the at least one material associated with the at least one of the fingerprint and the substrate to produce a computer generated image of the fingerprint. The mapping may include identifying an element in the chemical composition of the at least one material associated with the at least one of the fingerprint and the substrate; and assigning pixel intensities to the relative abundance of the element.